Figure 2.—

Scrambled Ure2 PFDs induce stable, dominant, and curable USA⁺ colonies. (A) Stability of the USA⁺ phenotype. USA⁺ colonies isolated upon overexpression of the wild-type Ure2 PFD, scrambled PFDs (URE2-21–25) or without overexpression (vector) were spotted onto YPAD and grown for 48 hr. Cells were then transferred to medium with uracil (right) or USA (left) to test for the ability to utilize USA. Shown are representative results, with six independent isolates inducing each PFD. (B) Dominance of the USA⁺ phenotype. USA⁺ colonies were spotted onto a lawn of [ure-o] cells of the opposite mating type and grown for 24 hr. Cells were replica plated to select for diploids and grown for 48 hr. Diploids were spotted onto medium with uracil (right) or USA (left) to test for the ability to utilize USA. Shown are representative results, from the same USA⁺ isolates as in A. (C) Curability of the USA⁺ phenotype. USA⁺ colonies were spotted onto YPAD supplemented with 5 mm guanidine HCl and grown for 48 hr. Cells were then spotted at low density onto fresh YPAD medium supplemented with 5 mm guanidine HCl and grown for an additional 48 hr. Cells were then transferred to medium with uracil (right) or USA (left) to test for the ability to utilize USA. Shown are representative results, from the same USA⁺ isolates as in A.